|2005 Model LeTourneau--unwrapping|
|Under the Load|
|Off and Away|
Once logs get to the mill they have to be unloaded. Now days when logs are hauled they are kept on the truck by a combination of stakes and 'wrappers'. Unlike other loads the logs are not tied to the truck. Instead they have a combination cable/chain that you simply wrap around the load and bind up with a chain binder. This holds the logs together as a bunch and then the bunch is contained on the truck by the stakes. There isn't a lot of agreement as to how many 'wrappers' are required. Lots of people make rules of such things. Oregon has had rules of a political origin for years requiring 4 wrappers while across the river in Washington State 3 wrappers safely get the job done. Don't try to make sense of it. The rules date back to the days when trucks either did not have stakes or had very short stakes.
Anyhow, one of the potential points of danger occurs when the load is 'unwrapped'. The logs may have shifted since loading and when the wrappers are removed the potential exists for a log to roll off the truck. The truck driver removing the wrapper is directly in harms way. He is standing of necessity right where the log will fall, and can't see it coming. The safety treatment for this issue is shown in the first photo. The stacker which will be unloading the logs first drives up and 'leans' on the truck. This provides a shield, so if a logs comes off the truck, it will hit the stacker instead of the truck driver.
Once the wrappers are removed the truck drivers moves to the front of the truck, and the stacker backs up, slips the tines under the load and clamps down on it with the top grabs and picks up the entire load and drives away with it. The logs will have to be scaled at some time. Some places use the less favored 'truck scale'. In this process the logs are measured or 'scaled' and graded while on the truck. Newer mills that have adequate space typically use a roll out scale in which after removal from the truck the logs are rolled out on the ground and the scaler's measure and grade them on the ground.
Fifty years ago and for the generation before that, logs made their final trip to the mill by water. Whether the logs were shipped by railroad or truck, they went to the water where they were rafted for final delivery to the mill. Even if they were hauled directly to the mill, there was usually a log dump near the mill. the truck or train would goto the dump where the logs would be cut loose from the truck and dumped into the water. Mills along major rivers would dump directly into the river, and mills on smaller water sources would have a mill pond to receive the logs. The logs floated in the mill pond and pond men with pike poles could easily sort the logs by pushing the floating logs around in the pond, like so many people might rearrange boats in a marina. This method allowed a few good men with pike poles and in the case of larger mills a few more men with 'water bulldozers' to dismantle the log rafts, and sort and arrange the logs in a manner suitable for entry into the mill for cutting. The mill pickup chain extended into the water so the pond man could simply push the logs over where the chain would catch them and start them on their way through the mill. However...
For the spec sheet on the current model LeTourneau stacker see here for a PDF file.
|Unloading in 2007|
|Older Stacker in 2002|
In the last 30 years environmental concerns about bark in the river and the like has fueled a trend toward 'dry lot mills'. When the drylot is used the logs have to be managed with brute force. This is where the log stacker comes in. Instead of dropping the stakes and letting the logs fall into the river, a fork lift is needed to unload the logs. This is where the LeTourneau comes in. it is designed to grab a load of logs and drive off with them. The capacity of this particular stacker is unknown to this writer, but these machines were typically made in 60, 80 and 120 thousand lb capacities. Since a typical truck load of logs weights from 50 to 60,000 lbs capacity is not an issue. The interesting thing about the LeToruneau design is that it is diesel electric. Hydraulics are not to be found on this machine. In a spin off of the technology used in diesel electric locomotives there are electric motors in the wheels, and the lifting is all done with racks, pinions and electric motors.